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Reports until 17:45, Monday 15 April 2019
H1 ISC
sheila.dwyer@LIGO.ORG - posted 17:45, Monday 15 April 2019 - last comment - 16:28, Tuesday 25 February 2020(48513)
modulation depths

This is just a summary so that this is written in one place in the log:

Koji measured the modulation depths for 9 and 45 MHz using an OSA after installing the new EOM: 41435  For the 9 MHz Koji measured gamma =0.191 for an epics setting of 23.6dBm, which is used during lock acquisition.  We reduce this in low noise to 20dBm, giving us the final modulation depth of 0.1352  (That is the whole story for 9MHz).

After that Daniel and company moved the EOM driver out of the PSL enclosure and added an RF combiner/amplifier, (41889) which increased the drive power for 45MHz by +1.83dBm compared to the time of Koji's measurement.  The modulation depth measured with an epics setting of 27dBm (used for lock acquisition) should have a modulation depth of 0.243 assuming the EOM response measured by Koji. In low noise we use an EPICS setting of 24dBm, so we should expect 0.172 modulation depth for 45 in full lock.   (These numbers are a little different from Daniels because he used the EOM response from G1800724 rather than Koji's measurement).

Craig and Georgia also measured modulation depths by exciting RFAM and measuring intensity noise after the OMC (47113) but those results aren't agreeing well with the numbers that Koji and Daniel posted. 

Comments related to this report
sheila.dwyer@LIGO.ORG - 16:28, Tuesday 25 February 2020 (55304)

The above is wrong!  Let me try again:

Koji measured the modulation depths for 9 and 45 MHz using an OSA after installing the new EOM: 41435 

9 MHz:

For the 9 MHz Koji measured gamma =0.191 radians for an epics setting of 23.6dBm, meaning that we are getting 0.220 rad/V.  Durring lock acquistion we are now using 23.4dBm out of the EOM driver, meaning that our acquisition modulation depth is now 0.189 rad, in low noise we are using 20.4dBm meaning that our modulation depth is 0.159 radians in low noise  

45 MHz:

Koji's measurement for 45 MHz indicates that 0.239 rad/V delivered to the EOM (which is different from the epics setting, which was 27dBm at that time).  After that Daniel and company moved the EOM driver out of the PSL enclosure and added an RF combiner/amplifier, (41889) which increased the drive power for 45MHz by +1.83dBm for the same epics setting compared to the time of Koji's measurement.  The modulation depth measured with an epics setting of 27dBm (used for lock acquisition) should have a modulation depth of 0.233 assuming the EOM response measured by Koji. In low noise we use an EPICS setting of 24dBm, so we should expect 0.177 modulation depth for 45 in full lock.   (These numbers are a little different from Daniels because he used the EOM response from G1800724 rather than Koji's measurement).

Craig and Georgia also measured modulation depths by exciting RFAM and measuring intensity noise after the OMC (47113) but those results aren't agreeing well with the numbers that Koji and Daniel posted. 

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